The mitral valve is one of the four valves of the heart having a complex structure. Various elements in the valve must function in a coordinated manner to cause blood to flow through the valve in an appropriate fashion. The mitral valve consists of two leaflets (anterior and posterior) that are attached to a fibrous ring (i.e., the annulus). The leaflets are anchored to papillary muscles in the wall of the left ventricle by a number of chordae tendineae (see, e.g., FIG. 1). As shown in FIGS. 1 and 2, a normal mitral valve annulus 10 has a posterior region and an anterior region situated between two trigones, which are fibrous structures that form part of the base of the heart. Under normal conditions, during the contraction phase of the heart (i.e., systole), the two leaflets come together (i.e., coapt) and close the valve, which inhibits blood flow from the ventricle into the aorta (i.e., regurgitation). The coaptation of the valve leaflets typically occurs at (or near) the level of the fibrous ring, in part due to the chordae tendineae which restrict the leaflets from rising above that level.
In mitral insufficiency of a degenerative origin, closure of the valve is insufficient because one of the leaflets (or both) moves above the plane of the annulus at least partially into the left atrium, causing what is commonly referred to as prolapse of the leaflets. One cause of prolapse is elongation or rupturing of one or more of the native chordae tendineae. One common technique for prolapse repair consists of use of artificial cords (i.e., “neocords”), often made of polytetrafluoroethylene (PTFE), to replace defective native chordae tendineae. These neocords are connected between the papillary muscles and a free edge of the leaflets and thus perform the function of the native chordae tendineae.
In mitral insufficiency, the valve annulus is often also dilated. In cases of severe mitral insufficiency, the patient often must undergo intervention to repair the valve or to replace the valve with an artificial valve prosthesis. A valve repair procedure typically has one or more of the following objectives: to restore the mobility of the leaflets without restriction or excess movement, to create an adequate coaptation surface or closure, and to remodel the shape and size of the dilated mitral annulus.